It is our aim to elucidate mechanisms of amino acid and alternative ethanol metabolism in man and experimental animals in order to understand the biochemical basis of metabolic disorders and alcoholism. We will carry out these experiments using stable isotopes, gas chromatography-mass spectrometry (GS/MS), and other analytical methods. Topics to be studied include: 1) Metabolism of L-(alpha-15N) lysine, L-(permittivity - 15N) lysine and D-(alpha-15N) lysine in hypoglycin-treated rabbits in vivo in order to determine the relative prevalence of the saccharopine- and pipecolic acid pathways. 2) Metabolism of (2S,3S)(3,4-13C2) isoleucine and (2S,3R)(3,4-13C2) isoleucine (alloisoleucine) in normal and hypoglycin-treated rats in order to determine if keto-enol tautomerization occurs to a signficant degree in isoleucine metabolism under physiological conditions. 3) Mechanism of conversion of methylmalongyl semialdehyde to propionate in rat liver mitochondria in vitro using proton- and 13C-NMR. 4) Establishment of a microanalytical method to quantitate the phenylketonuria intermediates using (luminous flux -2H5) labeled compounds as internal standards. This method will be used to quantitate these metabolites in amniotic fluids from pregnancy at risk to test whether or not this method can be used for the prenatal diagnosis of PKU. The same analysis will be done also in blood and urines from PKU heterozygotes in the postnatal studies. 5) Follow-up studies of patients with undefined organic acidemias or amnioaciduria using GC/MS. 6) Establishment of a microanalytical method of 2,3-butanediol using stable isotope dilution technique. 7) Quantitative analysis of 2,3-butanediol, an alternative metabolites of ethanol, in different strains of mice, having different preference to ethanol, to test whether this compound can be used as a genetic marker. 8) Study of biosynthesis of 2,3-butanediol in mice in vivo and in vitro using precursors labeled with stable isotopes.